Packet switched networks can route data traffic or packets of data using Internet Protocol networks. Voice over Internet Protocol (VoIP) allows voice traffic (e.g., telephone calls) to be carried over an Internet Protocol (IP) network between two telephones, computers, or similar communication devices.
The early stages of VoIP networks supported basic calls without any features. Such a VoIP network would typically have a call control element or simple softswitches responsible for basic routing and call detail recording. Later, vertical features such as call forwarding, incoming call screening, or click-to-dial were supported through the use of application logic resident on network elements such as more sophisticated softswitches or application servers. Advanced services such as Toll-Free or Virtual Private Networks or Pre-Paid Calling Card are now being supported in VoIP networks through the use of network-based application servers.
An alternative to the use of network-internal application servers for service and feature call control is the use of 3rd party, i.e., network-external, application servers, in which case some kind of gateway at the edge of the network is required to suitably manage the exchange of information between the external application server and the network. A gateway that uses the Session Initiation Protocol (SIP) to interface to both the call control element inside the network and to the external application server outside the network has many desirable characteristics such as network architectural simplicity, interface simplicity, and the opportunity for the 3rd party application service provider to utilize Session Initiation Protocol (SIP)-based application server equipment that is now common in the industry.
Such a Session Initiation Protocol (SIP)-based ‘external application gateway’ must address the control or regulation of sensitive or proprietary information that can be communicated from a particular network to an external application server. The SIP must ensure that control information coming from the external application server is within the scope of control allowed for that particular external application server and is applied to calls that external application server is permitted to control. The SIP must attach network-proprietary information to control messages from the external application server that is needed by other network-internal elements. Current descriptions of gateway support for external application servers do address any specifics of how a SIP-based gateway controls the information flow between the external application server and the network call control element.
Thus, a need exists for a telecommunications system and method to provide application-level control of the exchange of information through a gateway using SIP both toward external application servers and toward the call control element of a particular network.
The embodiments meet these needs.